1. Field of the Invention
The present invention relates to an electrophotographic copying machine adapted to produce copies with a margin at the leading end of each sheet of copy paper and give improved transport characteristics to its transport system for the transfer of copy images.
2. Description of the Prior Art
When toner is deposited on the leading end of copy paper, the system for transporting the copy paper fails to exhibit the desired transport characteristics and to transport the copy paper properly, so that conventional copying machines are adapted to intentionally form a minimum margin at the leading end of the copies produced. More specifically, a white plate of specified width is provided at the position where the leading end portion of the original laps over the plate, and the white plate is exposed to light before the original to form the margin at the leading end of the copy paper.
However, when an original is copied with such a copying machine on a reduced or enlarged scale, there arises a problem in that the margin is also reduced or enlarged at the same time. Accordingly, others have attempted to control paper feed timing by detecting the magnification so as to form margins of a constant width even at varying magnifications (see, for example, Unexamined Japanese Patent Publication No. SHO 60-114882).
Nevertheless, the copying machine thus adapted not only requires means for detecting magnifications but also a complex program for computing the timing of the paper feed from the detected magnification and therefore has the problem of being complex in construction and expensive.
The main object of the present invention is to provide a copying machine which is adapted to form margins of a constant width at all times even at varying magnifications merely by control of the paper feed timing with a timer means for measuring a definite set time and which accordingly incorporates simple and inexpensive detecting means and control means.